Hydraulic fluid power systems are used to operate a variety of types of machinery. Hydraulic systems transmit and control power for operating machinery by forcing water, oil, or other liquid under pressure through a fluid circuit composed of fluid conducting lines. Hydraulic jacks, tools for applying torque, and other hydraulic tools and machinery may be operated at high fluid pressures, for example as high as 10,000 psi.
Fluid couplings for the fluid lines supplying pressurized fluid to tools and machinery typically comprise a generally cylindrical socket having an axial fluid flow passage, and a generally cylindrical plug also having an axial fluid flow passage. The socket is attached to one fluid line and the plug is attached to another fluid line. The plug is pushed into the socket to join the two lines and establish a single fluid flow passage between the two lines. The coupling may be freestanding or the plug or the socket may be mounted in a manifold or wall or otherwise secured within the tool or machinery.
For many years, a mechanical connection of the socket to the plug for preventing separation of the two coupling members was provided by a threaded sleeve connected to the socket, and mating threads on the plug, so that the sleeve could be screwed onto the plug. This provided a very secure connection, but making the connection and removing the plug from the socket required considerable time, and often required a wrench or the like for providing sufficient torque to screw and unscrew the sleeve.
Accordingly, designers developed quick-action fluid couplings that enable the plug to be connected to the socket simply by pushing the plug into the socket. Quick-action couplings thus enable connections to be made quickly and without tools. Generally, a quick-action socket has a plurality of circumferentially spaced locking balls contained in apertures arranged in a circle around the plug-receiving end of the socket. A spring-biased detent sleeve circumscribing the socket can be axially moved so as to push the locking balls radially inwardly through the apertures. The plug has an annular groove to receive the portions of the locking balls that protrude through the apertures. When the plug is inserted into the socket and the locking balls are received in the groove in the plug, the locking balls prevent the plug from being pulled out of the socket. The plug is disconnected from the socket by sliding the detent sleeve so that the balls are free to move back through the apertures.
Various types of such quick-action fluid couplings have been developed, including the flat-face or flush-face coupling. In a flat-face coupling, the plug and socket are designed such that when the plug is disconnected from the socket, both the plug and socket present flat end faces. Thus, there are no recesses in the ends of the plug or socket in which fluid can collect and subsequently drip from after the coupling has been disconnected. The flat-face coupling also enables the coupling to be connected and disconnected without leakage while the fluid in the lines is under pressure.
A typical socket for a flat-face coupling is depicted in U.S. Pat. No. 5,123,446. The socket or female part includes a valve stem that terminates at one end in a valve head. A valve sleeve is sleeved over the valve and is larger in inside diameter than the outside diameter of the valve stem such that a space for conducting fluid through the socket is defined in the annular region between the valve sleeve and the valve stem. The valve sleeve is slidably disposed within a tube and an adapter is screwed into a rear end of the tube. The tube and adapter together define an internal fluid passage that feeds fluid from a fluid line attached to the adapter into the annular space between the valve stem and valve sleeve. When the female part is disconnected from the plug or male part, the forward end of this annular space is closed by engagement between the forward end of the valve sleeve and the valve head of the valve stem, with the aid of an O-ring surrounding the valve head. The valve sleeve is constantly urged forward to close the fluid flow path by a spring whose rear end abuts a shoulder defined at the end of the adapter. The valve stem is held stationary by a spider disposed in the passage of the female part. The spider has a central hole and the rear end of the valve stem extends through this hole. The rear end of the valve stem is threaded, and an acorn nut is secured to the threaded end to restrain the valve stem from moving axially in the forward direction. Axial movement of the valve stem in the rearward direction is prevented by a conical flared portion of the valve stem abutting the spider. When the male part is pushed into the female part, the valve sleeve is pushed rearwardly by a portion of the male part, and the valve stem in the female part opens a valve in the male part, so that a continuous fluid flow path is created between the female part and the male part. The spider includes apertures through which the fluid flows.
To ensure proper operation of the socket valve, it is important that the valve stem be rigidly affixed within the socket. In a conventional flat-face socket such as exemplified in the '446 patent, the valve stem is secured by a spider. In some cases, as in the '446 patent, the valve stem is externally threaded on its end and a nut is screwed onto the end of the stem to secure it to the spider, or the spider itself is internally threaded and is screwed onto the threaded end of the valve stem. A drawback of this approach is that the threads on the valve stem can easily be damaged during handling prior to assembly, thereby requiring reworking the stem or scrapping it altogether.
In other flat-face sockets, the end of the valve stem is passed through a central hole in the spider and is then swaged to prevent the stem from being separated from the spider. This has the disadvantage that if the valve stem becomes damaged or worn so as to require replacement, the valve stem cannot easily be replaced without special tools; accordingly, the entire assembly of valve stem and spider is typically replaced as a unit. Furthermore, the assembly of the valve stem with the spider requires specialized tooling for swaging the end of the valve stem.